Centrifugal compressor



June 8, 1937. B. HOFFMANN CENTRIFUGAL COMPRESSOR Filed April 25, 1935 Inventor. I

Bruno Hoffinann,' I357? His bbor'neg.

Patented June 8, 1937 UNITED STATES CENTRIFUGAL CQIVIPRESSOR Bruno Hofimann, Berlin, Germany, assignor to General Electric Company,

New York Application a corporation of April 25, 1935, Serial No. 18,203 Germany May 12, 1934 3 Claims. (01. 230-114) The present invention relates to centrifugal compressors or blowers, more specifically to the kind of compressors in which the output is controlled by valve means disposed in the inlet or suction conduit of the compressor. The provision of such valve means serves to restrict the eifective opening area in the suction conduit in order to change the flow of air or like gas from the atmosphere or like low pressure source to the compressor. The restriction of the opening area in many cases leads to pulsation and also causes a considerable increase in velocity of the medium flowing through the suction conduit. In the ordinary arrangement the available energy due to such increased velocity is lost.

The object of my invention is to provide an improved construction and arrangement of the type of compressors specified above whereby the output of the compressor may be effectively controlled, pulsations reduced and the efficiency increased. This is accomplished in accordance with my invention by the provision of means for throttling the supply in the inlet conduit, which means is arranged to form a nozzle or diffuser in order to transform the increased velocity of the throttled medium into pressure whereby the available energy of the high velocity medium is regained. The nozzle or difiuser may be formed by adjustable walls of the inlet or the suction conduit or of the casing near the entrance to the suction conduit. A particularly simple arrangement is obtained by the provision of a vane or adjustable wall which in combination with an oppositely lying wall portion of the inlet conduit forms a 35 diffuser.

In the accompanying drawing, which shows two embodiments of my invention, Fig. 1 is a somewhat diagrammatic view of a suction conduit of a compressor in accordance with my in- 40 vention; Fig. 2 illustrates a modification of my invention; and Fig. 8 is an enlarged sectional view along line 3-3 of Fig. 2.

The arrangement shown in Fig. 1 comprises an inlet or suction channel l0 having spaced-apart 45 longitudinal recesses H and I2 on opposite sides. Two difiuser walls I3 and I4 are disposed on opposite sides within the channel Ill. The upper ends of the walls l3 and M are disposed within the recesses II and secured to the walls of the 50 channel ID by means of pivots l5 and I6 respectively. The lower ends'of the walls I3 and [4 are bent outward and project into the recesses l2 of the opposite walls of the channel 10. Intermediate portions of the walls I3 and M are se- 55 cured to the ends of adjustable bolts l1 and I8 respectively. These bolts are screwed into wall portions of the channel I!) to permit positioning. of the diffuser walls 13 and M. The dash-dotted lines l9 and. indicate the positioning of the diffuser walls in which they form a maximum opening area. Other dash-dotted lines 2| and 22 indicate the difiuser walls in a position in which they considerably restrict the effective opening area of the inlet'conduit, that is, during low load and starting condition of the compressor. During operation of the compressor air or like gas at relatively low pressure is forced into the inlet channel in the direction of the arrows. Small effective opening area of the'diffuser causes an increase in velocity of the air stream. The increased velocity as it passes through the diffuser is transformed into pressure. The arrangement, as stated above, thereby increases the efficiency of the compressor, reduces pulsations during low load and provides for a smooth, continuous flow of air or like mediumthrough the suction conduit.

The arrangement shown in Figs. 2 and 3 comprises a compressor 25 having an inlet channel 26 somewhat rectangular in section. The walls of the inlet channel include a front wall 21 and a rear wall 28. The rear wall is shaped to form a recess 29 for accommodating a vane or wall 30 adjustably held at its upper end by means of a pivot 3|. An intermediate portion of the vane 30 is connected by a pivot 32 to a link mechanism 33. The end of the link mechanism is securely held on arotatable shaft 34 which latter can be turned or adjusted externally of the inlet conduit. A packing 35 is secured to the rear wall 28 to reduce back flow of air or like medium through the recess 29. Another packing 36 is secured to the lower end of the vane 30 whereby complete sealing of the interior of the compressor may be effected when the lower end of the vane 38 with the packing 36 is moved into contact with the front wall 21. The end surfaces 31 of the vane 30 are machined'and disposed in close proximity to themachined end surfaces 38 of the side walls of the inlet conduit in order to reduce leakage between these adjacent surfaces, especially when the vane is in position to completely shut the inlet conduit. The complete sealing facilitates starting of the compress'or. In the present instance the vane 30 is shown in full lines in an intermediate position, in dash-dotted lines 39 in closed position, and in other dash-dotted lines 40 in full open position. The flow of air or like medium is indicated by arrows in Fig. 3. The vane 30 is moved towards closing position as the load demand decreases and during starting in order to reduce the effective opening area of the inlet conduit. The

velocity of the air as it passes through the'narrow portion of the diffuser formed by the vane 30 and the front wall 21,is increased, and the increased velocity energy thus obtained is transformed into pressure energy as the air passes through'thevwide flaring portion of the difiuser.

What I claim as new and Letters Patent of the United States, is V 1. A centrifugal compressor including a surftion conduit and a diffuser in the suction conduit for controlling the fiowf'o f a medium therethrough and for preventing a reduction in inletv pressure with decreasing load, said diffuser including amember having abortion fpivot'ally" secured to the wall of the suction conduit and" positioning'means connected to another portion of the member, movement of said member to diffuser action.

reduce the flow causing simultaneously increased 2. A centrifugal compressor includingfa suction conduit and a difiuser in'the suction conduit;

desire to secure by,

for controlling the flow r of a medium therethrough and for preventing a reduction ininlet pressure with decreasing load, said diffuser including a member having a portion pivotally secured .to the wall of the suction conduit, positioning means connected to another portion of the member, to move the member in order to reduce the effective cross-section of the conduit in response to decreasing load demand, and seal- ,ing means for reducing leakage of fluid into the compressor while said member is in closed posi tion. I

3 A centrifugal compressor including a suction-conduit substantiallyrectangular in cross section, two curved vanes having end portions pivotally held on opposite walls of the conduit,

1 and adjustable means connected to other portions of the vanes for-controlling'the effective 7 opening area of the conduit to effect increased diffusion with increased throttling in order to prevent reduction of theinlet pressure with decreasing load,. the conduit having recesses forming guides for thevanes: 1V i a BRUNO HoFr'MANN. 

